Hard alloy bar vacuum sintering process capable of preventing deformation

Abstract

The invention relates to the technical field of sintering, in particular to a deformation-preventing hard alloy bar vacuum sintering process which comprises the steps that S1, a hard alloy bar blank is prepared and subjected to degumming treatment; s2, the bar blank obtained after degumming is subjected to vacuum pumping treatment; and S3, sintering treatment is conducted on the vacuumized bar blank, and the heating rate in the sintering process is regulated and controlled. According to the method, the heating rate is dynamically adjusted based on the change conditions of the temperature and the heating rate in the sintering process, the problem that the finished product quality and the production efficiency of the hard alloy bar are reduced due to the fact that the furnace temperature is controlled only through the fixed heating rate is solved, and the finished product quality and the production efficiency of the hard alloy bar are improved.

Description

Technical Field

[0001] This application relates to the field of sintering technology, specifically to a vacuum sintering process for cemented carbide rods to prevent deformation. Background Technology

[0002] Cemented carbide is an alloy material made from hard compounds and binder metals. Due to its high hardness, good wear resistance, and high toughness, it is widely used in the field of cutting tool materials. Vacuum sintering has become the mainstream process for cemented carbide sintering due to its advantages such as high alloy densification and reasonable cost. However, since vacuum sintering furnaces mainly transfer heat through radiation and conduction, temperature gradients can occur within the furnace, potentially causing bending deformation of the sintered alloy. Therefore, it is necessary to optimize the existing sintering process to avoid bending deformation of cemented carbide bars.

[0003] Sintering furnace temperature control is crucial to the quality of cemented carbide bars produced. However, current technologies typically regulate furnace temperature by fixing heating parameters, failing to adequately consider the dynamic impact of differences in density and composition distribution among different batches of bar billets on the temperature gradient within the furnace. Furthermore, the degree of localized thermal stress accumulation in the bars varies due to the intensity of different temperature gradients. Therefore, controlling furnace temperature solely by fixing the heating rate reduces the finished product quality and production efficiency of cemented carbide bars. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a vacuum sintering process for cemented carbide rods to prevent deformation, thereby resolving the existing issues.

[0005] The vacuum sintering process for preventing deformation of cemented carbide rods in this application adopts the following technical solution: One embodiment of this application provides a vacuum sintering process for preventing deformation of cemented carbide rods, the process comprising the following steps: S1: Prepare cemented carbide rod blanks and perform degumming treatment; S2: Vacuum treatment is performed on the degummed bar stock; S3: The vacuum-sealed bar stock is sintered, and the heating rate during the sintering process is controlled, specifically as follows: The temperature at each preset height inside the sintering furnace is acquired in real time during each sintering process, where each height refers to the top, middle and bottom of the sintering furnace; Based on the dispersion of temperature at all heights in the sintering furnace at each moment during each sintering process, the moments with significant temperature differences in each sintering process are screened out; based on the proportion of all moments with significant temperature differences in the first heating stage in each sintering process, and combined with the dispersion of temperature at all heights in the sintering furnace at each moment with significant temperature differences in the first heating stage, the furnace temperature deviation factor of the first heating stage in each sintering process is determined. Based on the correlation between the temperature of the parts of the sintering furnace and the top and bottom at all times during the first heating stage in each sintering process, and the number of clusters obtained by clustering at all times with significant temperature differences during the first heating stage, and combined with the furnace temperature deviation factor, the temperature imbalance coefficient of the first heating stage in each sintering process is determined. A number of sintering processes prior to the current sintering process are clustered to obtain a good cluster. Based on the difference in temperature imbalance coefficient of the first heating stage between the current sintering process and all sintering processes in the good cluster, as well as the difference in heating rate in the middle of the sintering furnace, the temperature rise deviation coefficient of the first heating stage in the current sintering process is determined, so as to regulate the heating rate of the subsequent heating stages in the current sintering process.

[0006] Preferably, the vacuum level during the vacuuming process is in the range of 0.3 to 0.7 Torr.

[0007] Preferably, the heating time of the first heating stage is controlled at 55~60 minutes.

[0008] Preferably, the cooling rate during the cooling stage of the sintering process is in the range of 11~30℃ / min.

[0009] Preferably, the screening of moments with significant temperature differences during each sintering process includes: The degree of temperature dispersion at all heights inside the sintering furnace at each moment during each sintering process is recorded as the temperature dispersion value for each sintering process. The discrete temperature values ​​at all times during each sintering process are used as input to the threshold segmentation algorithm, and the output is the segmentation threshold. The times when the discrete temperature values ​​are greater than or equal to the segmentation threshold are taken as the times when the temperature difference is significant during each sintering process.

[0010] Preferably, the expression for the furnace temperature deviation factor during the first heating stage in each sintering process is: In the formula, This represents the furnace temperature deviation factor during the first heating stage in the i-th sintering process; This represents the percentage of all significant temperature differences during the first heating stage in the i-th sintering process out of all possible times. It represents the mean of the discrete values ​​of temperature at all significant temperature differences during the first heating stage in the i-th sintering process.

[0011] Preferably, the method for determining the temperature imbalance coefficient during the first heating stage in each sintering process is as follows: Calculate the cross-correlation sequence of temperatures between the middle part and the top and bottom of the sintering furnace at all times during the first heating stage in each sintering process. The time delay corresponding to the maximum value in the cross-correlation sequence of temperatures between the middle and the top is denoted as the first time delay, and the time delay corresponding to the maximum value in the cross-correlation sequence of temperatures between the middle and the bottom is denoted as the second time delay. The difference between the first time delay and the second time delay is denoted as the time delay difference of the first heating stage in each sintering process. The number of clusters obtained by clustering all significant temperature differences during the first heating stage is denoted as the cluster number. The product of the time lag difference of the first heating stage and the furnace temperature deviation factor in each sintering process is multiplied by the cluster number, and the result is used as the temperature imbalance coefficient of the first heating stage in each sintering process.

[0012] Preferably, the step of clustering a preset number of sintering processes prior to the current sintering process to obtain a good cluster includes: Obtain the deformation rate of the bar at the end of each sintering process, cluster the sintering processes that were previously sintered a preset number of times, where the metric distance of the clustering process is set to the absolute value of the difference in the deformation rate of the bar between sintering processes, output all clusters, calculate the mean value of the deformation rate of the bar in all sintering processes within each cluster, and record it as the mean deformation rate. The cluster corresponding to the minimum mean deformation rate is taken as the good cluster of the current sintering process.

[0013] Preferably, the expression for the temperature rise deviation coefficient during the first heating stage in the current sintering process is: In the formula, This represents the temperature rise deviation coefficient during the first heating stage of the current sintering process; This represents the minimum difference in temperature imbalance coefficients during the first heating stage between the current sintering process and all subsequent sintering processes in the good cluster; This represents the average difference in heating rate at the center of the sintering furnace between the current sintering process and all subsequent sintering processes in the good cluster.

[0014] Preferably, the regulation of the heating rate in the subsequent heating stages of the current sintering process includes: The heating rate of the next heating stage after the first heating stage in the current sintering process The expression is: In the formula, This indicates the preset initial heating rate for the next heating stage after the first heating stage in the current sintering process; This indicates the preset rate adjustment value; This represents the temperature rise deviation coefficient during the first heating stage of the current sintering process; norm() represents the normalization function; The heating rate is iterated according to the above-mentioned process of adjusting the heating rate of the next heating stage, and all heating stages after the first heating stage in the current sintering process are traversed and the heating rate is adjusted accordingly.

[0015] This application has at least the following beneficial effects: This application first constructs a furnace temperature deviation factor based on the proportion of all significant temperature differences during the first heating stage in each sintering process, and combines this with the dispersion of temperature at all heights within the sintering furnace at each significant temperature difference during the first heating stage. This comprehensively evaluates the frequency and intensity of temperature inhomogeneity within the sintering furnace during the first heating stage, achieving a quantitative characterization of the risk of thermal stress accumulation. This provides a basis for subsequent dynamic adjustment of the heating rate, thereby helping to effectively prevent deformation of the bars caused by temperature gradients and significantly improving sintering quality and production efficiency. Furthermore, this application combines time lag differences, furnace temperature deviation factor, and cluster size... By constructing a temperature imbalance coefficient, the degree of temperature non-uniformity in the sintering furnace during the first heating stage is accurately quantified, effectively distinguishing between actual thermal stress risk and impurity interference error. This guides the dynamic optimization of subsequent heating rates, significantly reducing the risk of bar deformation and improving sintering quality and production efficiency. Finally, by combining historical good sintering process data, this application constructs a temperature rise deviation coefficient to dynamically assess the degree of deviation between the current sintering process and historical optimal conditions, and intelligently adjusts the heating rate of subsequent heating stages accordingly. This effectively reduces the risk of thermal stress accumulation caused by temperature gradients and improves the sintering quality and production efficiency of cemented carbide bars. Attached Figure Description

[0016] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A flowchart illustrating the steps of a vacuum sintering process for preventing deformation of cemented carbide rods, as provided in one embodiment of this application. Figure 2 A flowchart illustrating the steps for controlling the heating rate according to one embodiment of this application. Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by this application to achieve the intended purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a vacuum sintering process for preventing deformation of cemented carbide rods proposed in this application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0019] Unless otherwise defined, terms such as “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a circuit structure, article, or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the article or device that includes said element. Furthermore, the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The following detailed description, in conjunction with the accompanying drawings, illustrates a specific scheme of a vacuum sintering process for preventing deformation of cemented carbide rods provided by this application.

[0020] The following describes in detail, with reference to the accompanying drawings, a specific scheme for a vacuum sintering process for preventing deformation of cemented carbide rods provided in this application.

[0021] Example 1 Example 1 provides a vacuum sintering process for preventing deformation of cemented carbide rods. For details, please refer to [link / reference]. Figure 1 The method includes the following steps: S1: Prepare cemented carbide rod blanks and perform degumming treatment.

[0022] The uniformly mixed and well-adhesive-added cemented carbide raw material is fed into an extruder. Cemented carbide billets are prepared according to the billet die and subjected to natural disturbance treatment. Then, the billets are placed in a degumming furnace and degummed by hydrogen gas. After degumming, the billets are naturally cooled to room temperature.

[0023] S2: Vacuum treatment is performed on the degummed bar stock.

[0024] The degummed rod blanks are cut to a set length using a diamond grinding wheel. An anti-stick coating is then applied to the graphite boat containing the rod blanks, and the boat is allowed to dry naturally in a ventilated environment. The graphite boat containing the rod blanks is then placed in a vacuum sintering furnace, and a vacuum process is performed. In this embodiment, the vacuum level inside the sintering furnace is 0.3 Torr.

[0025] S3: The vacuum-sealed bar stock is sintered, and the heating rate during the sintering process is controlled.

[0026] After completing the vacuuming operation in step S2, the sintering operation is carried out. First, the temperature of the sintering furnace is raised from room temperature to 600℃. In this embodiment, the heating time is set to 55 minutes, and the temperature is held at 600℃ for 30 minutes. Then, the temperature is raised to 800℃ and held at 800℃ for 20 minutes. Next, the temperature is raised to 1350℃ and held at 1350℃ for 30 minutes. Then, the temperature is further lowered to 1250℃. In this embodiment, the cooling rate is 11℃ / min. When the temperature reaches 1250℃, it is raised to 1450℃ and held at 1450℃ for 40 minutes. Finally, after the holding at 1450℃ is completed, the vacuum sintering furnace is powered off, and the cemented carbide rod blank is cooled to room temperature with the furnace while maintaining the vacuum. The sintering preparation of the cemented carbide rod is completed.

[0027] The furnace temperature control of the sintering furnace is crucial to the production quality of cemented carbide bars. However, existing technologies typically adjust the furnace temperature by fixing the heating rate, without fully considering the dynamic impact of differences in density and composition distribution of bar blanks from different batches on the temperature gradient within the furnace, as well as the varying degrees of local thermal stress accumulation caused by different temperature gradient intensities. Therefore, controlling the furnace temperature solely by fixing the heating rate can affect the finished product quality of the bars, easily leading to bending and deformation, and resulting in poor sintering performance.

[0028] Therefore, to solve the above problems, this embodiment analyzes the changes in temperature and heating rate during historical sintering processes and controls the heating rate in the current sintering process. The flowchart of the heating rate control steps provided in this embodiment is as follows: Figure 2 As shown, the specific process of controlling the heating rate is as follows: S301: Real-time acquisition of the temperature at preset heights inside the sintering furnace during each sintering process, where each height refers to the top, middle, and bottom of the sintering furnace.

[0029] In a vacuum sintering process of cemented carbide rods, the temperature at each preset height in the sintering furnace during each sintering process is collected in real time by three temperature thermocouples. The heights are the top, middle and bottom of the sintering furnace. All temperature data are collected synchronously and in real time. The data collection frequency is set to f, and the collection time is from the start to the end of each sintering process.

[0030] It should be noted that the data acquisition frequency f is set manually. In this embodiment, the data acquisition frequency f is 0.2Hz. In actual applications, as other implementation methods, implementers can also set it according to specific circumstances. This embodiment does not impose any special restrictions.

[0031] It should be noted that the top temperature is the temperature at the center of the top of the sintering furnace. Similarly, the middle temperature and the bottom temperature are the temperatures at the center of the middle and the center of the bottom of the sintering furnace, respectively.

[0032] S302: Based on the dispersion of temperature at all heights in the sintering furnace at each moment during each sintering process, the significant temperature difference moments in each sintering process are screened out; based on the proportion of all significant temperature difference moments in the first heating stage in each sintering process, and combined with the dispersion of temperature at all heights in the sintering furnace at each significant temperature difference moment in the first heating stage, the furnace temperature deviation factor of the first heating stage in each sintering process is determined.

[0033] Since the graphite heating tubes inside the vacuum sintering furnace are evenly distributed around the furnace, theoretically, the internal heating temperature should be centrally symmetrical, with the temperature at the top and bottom of the furnace being relatively consistent and eventually aligning with the center temperature after a period of time. However, because the vacuum sintering furnace primarily heats through non-contact radiation, heat transfer from the periphery to the center takes time. Furthermore, the heat transfer process is affected by the shielding effect of the bar stock. The differences in internal density and composition distribution among bar stock from different extrusion batches further lead to variations in the intensity and duration of the temperature gradient within the furnace.

[0034] The greater the intensity and duration of the temperature gradient, the greater the potential accumulation of local thermal stress in the bar stock during the current sintering process. This necessitates adjustments to the subsequent heating rate to prevent further impact on the bar's sintering quality. Therefore, this embodiment uses the dispersion of temperature at all heights within the sintering furnace at each moment during each sintering process to identify significant temperature differences. Based on the pre-defined proportion of significant temperature differences during the first heating stage in each sintering process, and combined with the dispersion of temperature at all heights within the sintering furnace at each significant temperature difference moment within the first heating stage, a furnace temperature deviation factor for the first heating stage in each sintering process is determined. This factor assesses the degree to which the temperature distribution within the sintering furnace deviates from the ideal uniformity, indirectly reflecting the risk of thermal stress accumulation within the bar. Furthermore, adjusting the heating rate helps avoid the impact of thermal stress accumulation on the bar's sintering quality. The specific process for obtaining the furnace temperature deviation factor is as follows: In this embodiment, firstly, based on the dispersion of temperature at all heights within the sintering furnace at each moment during each sintering process, the moments with significant temperature differences during each sintering process are screened out. Specifically: In this embodiment, the degree of temperature dispersion at all heights in the sintering furnace at each moment during each sintering process is recorded as the temperature dispersion value for each sintering process. The temperature dispersion value reflects the difference between the top temperature, bottom temperature, and middle temperature in the sintering furnace at the same moment. The larger the temperature dispersion value, the greater the temperature non-uniformity in the sintering furnace at the same moment, and the more likely it is to cause local thermal stress accumulation in the bar.

[0035] It should be noted that there are many methods to measure the dispersion of a set of data. In this embodiment, the standard deviation of the temperature at all heights in the sintering furnace at each moment during each sintering process is recorded as the dispersion of the temperature at all heights in the sintering furnace at each moment during each sintering process. In practical applications, implementers may also use other methods such as variance or coefficient of variation to measure the dispersion of data, depending on the specific circumstances. This embodiment does not impose any special restrictions on the selection of methods for measuring the dispersion of data.

[0036] The discrete temperature values ​​at all times during each sintering process are used as the input to the threshold segmentation algorithm, and the output is the segmentation threshold. The times when the discrete temperature values ​​are greater than or equal to the segmentation threshold are taken as the times when the temperature difference is significant during each sintering process. The times when the temperature difference is significant reflect the times when the temperature gradient inside the sintering furnace is relatively intense during the first heating stage.

[0037] It should be noted that there are many commonly used threshold segmentation algorithms. In this embodiment, the Otsu threshold segmentation algorithm is used to filter out moments with significant temperature differences. In practical applications, as other implementation methods, implementers may also use other threshold segmentation algorithms according to specific circumstances. This embodiment does not impose any special restrictions on the selection of threshold segmentation algorithms.

[0038] Among them, the Otsu threshold segmentation algorithm is a well-known technique, and the specific process of using it to obtain the moment of significant temperature difference will not be described in detail.

[0039] Furthermore, this embodiment determines the furnace temperature deviation factor for the first heating stage in each sintering process based on the proportion of all significant temperature differences during the first heating stage, and in conjunction with the temperature dispersion at all heights within the sintering furnace at each significant temperature difference during the first heating stage. Specifically: As one implementation method, in this embodiment, the furnace temperature deviation factor during the first heating stage in the i-th sintering process is... The expression is: In the formula, This represents the percentage of all significant temperature differences during the first heating stage in the i-th sintering process out of all possible times. It represents the mean of the discrete values ​​of temperature at all significant temperature differences during the first heating stage in the i-th sintering process.

[0040] It should be further explained that, in this embodiment, the period between the temperature inside the sintering furnace rising from room temperature to the aforementioned 600°C and the end of the holding period at 600°C during each sintering process is defined as the first heating stage of each sintering process.

[0041] Based on the furnace temperature deviation factor of the first heating stage in each sintering process, it can be understood that the furnace temperature deviation factor reflects the degree of influence of the uneven temperature inside the sintering furnace during the first heating stage. If the proportion of all significant temperature differences in the first heating stage during the i-th sintering process is larger, it indicates that the uneven temperature phenomenon inside the sintering furnace occurs more frequently during the first heating stage in the i-th sintering process, and the corresponding first furnace temperature deviation factor is relatively larger. This indicates that the uneven temperature inside the sintering furnace is more severe and lasts longer during the first heating stage in the i-th sintering process, and the deviation from the sintering furnace temperature under normal heating stage may be greater. Therefore, in subsequent sintering processes, it is more necessary to adjust the heating rate more significantly to alleviate the problem of local stress concentration caused by temperature gradient and reduce the risk of deformation of the bar. Conversely, if the proportion of significant temperature differences during the first heating stage in the i-th sintering process is smaller than that of all other times, it indicates that the temperature non-uniformity in the sintering furnace is less significant during the first heating stage in the i-th sintering process, and the corresponding first furnace temperature deviation factor is relatively smaller. This means that the temperature distribution in the sintering furnace is relatively uniform and stable during the first heating stage in the i-th sintering process, and the deviation from the ideal uniform sintering furnace temperature is smaller. Therefore, the adjustment range of the heating rate in subsequent sintering processes can be relatively small, and it can even maintain the preset heating rate for sintering. This helps to improve production efficiency and shorten the sintering cycle while ensuring sintering quality.

[0042] Thus, this embodiment comprehensively evaluates the frequency and intensity of temperature unevenness in the sintering furnace during the first heating stage by constructing a furnace temperature deviation factor, thereby achieving a quantitative characterization of the risk of thermal stress accumulation and providing a basis for subsequent dynamic adjustment of the heating rate. This helps to effectively prevent deformation of the bars caused by temperature gradients and significantly improves sintering quality and production efficiency.

[0043] S303: Based on the correlation between the temperature of the parts of the sintering furnace and the top and bottom at all times during the first heating stage in each sintering process, and the number of clusters obtained by clustering at all times with significant temperature differences during the first heating stage, and combined with the furnace temperature deviation factor, determine the temperature imbalance coefficient of the first heating stage in each sintering process.

[0044] Since the sintering quality of cemented carbide bars is also affected by factors such as precipitated particles and water vapor dust in the sintering furnace, and the precipitation time, degree, and movement direction of these particles and water vapor dust are irregular, the temperature data collected at the top, bottom, or center of the sintering furnace at a certain moment may fluctuate instantaneously. This can lead to significant temperature differences between the three locations even under uniform temperature conditions, resulting in a large temperature dispersion at that moment. Therefore, assessing temperature uniformity solely through the temperature deviation factor will introduce errors. This embodiment, based on the correlation between the temperatures of the sintering furnace and the top and bottom at all moments during the first heating stage of each sintering process, and the number of clusters obtained by clustering all moments with significant temperature differences during the first heating stage, combined with the furnace temperature deviation factor, determines the temperature imbalance coefficient for the first heating stage of each sintering process to more accurately determine the temperature uniformity within the furnace during the heating stage. The specific process is as follows: If the degree of shielding by the bar material is inconsistent between the top and bottom regions when transferring heat to the central area, it will also lead to asynchronous temperature changes between the top, bottom, and central regions, resulting in uneven temperature distribution within the furnace. Although the instantaneous temperature difference caused by asynchronous heating may be small, continuous asynchronous heating will also generate uneven thermal stress.

[0045] Based on the above analysis, this embodiment calculates the cross-correlation sequences of temperatures between the middle part and the top and bottom of the sintering furnace at all times during the first heating stage in each sintering process. The time lag corresponding to the maximum value in the cross-correlation sequence between the middle and the top is denoted as the first time lag, and the time lag corresponding to the maximum value in the cross-correlation sequence between the middle and the bottom is denoted as the second time lag. The difference between the first and second time lags is denoted as the time lag difference in the first heating stage of each sintering process. This reflects whether the influence of the top and bottom on the center temperature is consistent. The larger the time lag difference, the more inconsistent the influence, and the more asynchronous the heat transfer from the top and bottom to the center region is in time.

[0046] It should be noted that the process of obtaining the cross-correlation sequence is a well-known technique. Each element in the cross-correlation sequence represents the cross-correlation coefficient between the middle part and the top and bottom temperatures under different time delays. The time delay k ranges from [value missing]. In this embodiment, m is 180, and k is incremented by 1.

[0047] It should be understood that there are many methods to measure the difference between data. In this embodiment, the absolute value of the difference is used to determine the difference between data. For example, in this embodiment, the absolute value of the difference between the first time lag and the second time lag is taken as the difference between the first time lag and the second time lag. In actual application, as other implementation methods, implementers may also use other methods such as the square or ratio of the difference to measure the difference between data in combination with the specific situation. This embodiment does not impose any special restrictions on the selection of methods to measure the difference between data.

[0048] It should be noted that, unless otherwise specified, all methods in this embodiment that involve measuring differences between data use the method of taking the absolute value of the difference.

[0049] Furthermore, during the heating phase, the temperatures at the top and bottom of the furnace are relatively consistent at the beginning of the heating process, and both differ from the temperature at the center. As heat is conducted, the temperature inside the furnace gradually becomes uniform, and the temperature dispersion should gradually decrease. Therefore, if the sintering process of the bar is not affected by impurities such as precipitated particles and water vapor, the temperature dispersion should change from large to small and then tend to stabilize. Thus, all significant temperature differences should have high aggregation.

[0050] Therefore, based on the above analysis, this embodiment will cluster the number of clusters obtained by clustering at all significant temperature differences during the first heating stage, and record this as the number of clusters. It should be noted that there are many commonly used clustering algorithms. In this embodiment, the k-means clustering algorithm is used to cluster the moments with significant temperature differences. The metric distance is set as the time interval between moments with significant temperature differences, the elbow rule is used to obtain the number of clusters, and all clusters are output.

[0051] Among them, the k-means clustering algorithm and the elbow rule are well-known techniques. The specific process of using the k-means clustering algorithm to cluster at times of significant temperature difference and the specific process of using the elbow rule to determine the number of clusters will not be described in detail.

[0052] It should be noted that the number of clusters reflects the high degree of aggregation among all significant temperature differences. The larger the number of clusters, the worse the aggregation, and the more dispersed the distribution of significant temperature differences. This indicates that the collected temperature is more likely to be affected by precipitated particles or water vapor, and thus reflects a larger error in the furnace temperature deviation factor calculated at this time. Conversely, the smaller the number of clusters, the less error interference the furnace temperature deviation factor is subjected to during calculation, and the more accurate the furnace temperature non-uniformity is reflected.

[0053] Furthermore, in this embodiment, the product ratio of the time lag difference of the first heating stage in each sintering process and the furnace temperature deviation factor, plus the number of clusters, is used as the temperature imbalance coefficient of the first heating stage in each sintering process.

[0054] Based on the temperature imbalance coefficient during the first heating stage of each sintering process, it can be understood that the temperature imbalance coefficient characterizes the degree of temperature unevenness within the sintering furnace during the first heating stage. A larger time lag difference during the first heating stage indicates a significant time asynchrony in heat transfer from the top and bottom of the sintering furnace to the middle, suggesting a substantial delay in heat transfer between the upper and lower parts of the furnace. This can lead to uneven heating of the bars, resulting in a larger corresponding temperature imbalance coefficient. Simultaneously, a larger furnace temperature deviation factor during the first heating stage indicates a more frequent occurrence of temperature unevenness within the sintering furnace. The more complex and intense the process, the larger the corresponding temperature imbalance coefficient. Furthermore, if the number of clusters in the first heating stage of the current sintering process is smaller, it indicates that the distribution is highly concentrated when the temperature difference is significant, indicating that the temperature non-uniformity is real and not due to impurities. Therefore, the corresponding temperature imbalance coefficient is relatively large. A large temperature imbalance coefficient reflects a greater degree of temperature non-uniformity in the furnace and that it is not affected by significant impurities. The more accurate the measurement of furnace temperature non-uniformity, the greater the thermal stress accumulated in the bar billet during the first heating stage, and the greater the need to adjust the heating rate in subsequent heating stages. Conversely, the smaller the time lag difference in the first heating stage of the current sintering process, the more synchronous the heat transfer from the top and bottom to the middle of the sintering furnace is in time, resulting in uniform heating of the upper and lower parts of the furnace and a smaller corresponding temperature imbalance coefficient. Simultaneously, the smaller the furnace temperature deviation factor in the first heating stage of the current sintering process, the lower the frequency and intensity of temperature unevenness within the sintering furnace, leading to a relatively stable temperature distribution and thus a smaller corresponding temperature imbalance coefficient. Furthermore, the larger the number of clusters in the first heating stage of the current sintering process, the more significant the temperature difference distribution. The presence of a small temperature imbalance coefficient indicates that the temperature unevenness may be affected by impurities or accidental factors, resulting in a lower reliability of the furnace temperature imbalance measurement. Consequently, the corresponding temperature imbalance coefficient is relatively small. A small temperature imbalance coefficient reflects a less severe degree of temperature unevenness in the furnace or a larger measurement error, indicating a lower reliability of the furnace temperature unevenness measurement. This suggests that the risk of accumulated thermal stress in the bar billet during the first heating stage is relatively small. In subsequent heating stages, the adjustment range of the heating rate can be appropriately reduced, or even the original heating rate can be maintained, which helps to improve production efficiency while ensuring sintering quality.

[0055] Thus, this embodiment constructs a temperature imbalance coefficient by combining time lag difference, furnace temperature deviation factor and cluster number, which accurately quantifies the degree of temperature non-uniformity in the first heating stage of the sintering furnace, effectively distinguishes between real thermal stress risk and impurity interference error, thereby guiding the dynamic optimization of subsequent heating rate, significantly reducing the risk of bar deformation and improving sintering quality and production efficiency.

[0056] S304: Clustering of a preset number of sintering processes prior to the current sintering process yields favorable clusters. Based on the differences in temperature imbalance coefficients during the first heating stage between the current sintering process and all sintering processes within these favorable clusters, as well as the differences in heating rates at the center of the sintering furnace, the temperature rise deviation coefficient for the first heating stage in the current sintering process is determined. This is used to regulate the heating rate of subsequent heating stages in the current sintering process. This embodiment optimizes the current sintering process by combining historical sintering process data showing lower bar deformation rates. The specific process is as follows: In this embodiment, a preset number of sintering processes prior to the current sintering process are used as input to the clustering algorithm. The metric distance of the clustering process is set as the absolute value of the difference in bar deformation rate between sintering processes. The elbow rule is used to determine the number of clusters. All clusters are output. The mean value of bar deformation rate in all sintering processes within each cluster is calculated and recorded as the mean deformation rate. The cluster corresponding to the minimum mean deformation rate is taken as the good cluster of the current sintering process.

[0057] It should be noted that the preset quantity is set manually. In this embodiment, the preset quantity is 200. In actual applications, as other implementation methods, implementers can also set it according to specific circumstances. This embodiment does not impose any special restrictions.

[0058] In this embodiment, the k-means clustering algorithm is used to cluster the sintering process. In actual applications, implementers can also set their own algorithm according to specific circumstances. This embodiment does not impose any special restrictions.

[0059] Furthermore, this embodiment determines the temperature rise deviation coefficient of the first heating stage in the current sintering process based on the difference in temperature imbalance coefficient between the current sintering process and all subsequent sintering processes in the good cluster, as well as the difference in heating rate in the middle of the sintering furnace. Specifically: As one implementation method, in this embodiment, the temperature rise deviation coefficient during the first heating stage of the current sintering process is... The expression is: In the formula, This represents the minimum difference in temperature imbalance coefficients during the first heating stage between the current sintering process and all subsequent sintering processes in the good cluster; This represents the average difference in heating rate at the center of the sintering furnace between the current sintering process and all subsequent sintering processes in the good cluster.

[0060] The method for calculating the heating rate is a well-known technique, and its specific calculation process will not be elaborated here.

[0061] Based on the temperature rise deviation coefficient during the first heating stage of the current sintering process, it can be understood that the temperature rise deviation coefficient reflects the degree of deviation between the current sintering process and historically successful sintering processes during the first heating stage. The larger the minimum difference in temperature imbalance coefficients between the current sintering process and all subsequent sintering processes within the successful cluster, the greater the difference between the current sintering process's temperature imbalance coefficient and that of historically successful sintering processes. This indicates a significant deviation of the current furnace temperature uniformity from historically excellent levels, a high risk of thermal stress, and a correspondingly larger temperature rise deviation coefficient. Simultaneously, if the current... The greater the average difference in heating rate at the center of the sintering furnace between the sintering process and all sintering processes in the good sintering cluster, the more significant the difference between the current sintering process's heating rate and the average of the good sintering process. The heating strategy may be too fast or too slow, which can easily lead to thermal stress problems, and the corresponding temperature rise deviation coefficient is larger. The larger the temperature rise deviation coefficient, the greater the possibility that the bar has accumulated thermal stress in the first heating stage of the current sintering process. Therefore, in the subsequent heating stages, it is more necessary to adjust the heating rate to a greater extent to alleviate the stress concentration problem caused by uneven furnace temperature and reduce the risk of bar bending deformation. Conversely, if the minimum difference in temperature imbalance coefficient between the current sintering process and all subsequent sintering processes in the good cluster during the first heating stage is smaller, it indicates that the temperature imbalance coefficient of the current sintering process is close to that of a historical good sintering process, the current furnace temperature uniformity is well controlled, the risk of thermal stress is low, and the corresponding temperature rise deviation coefficient is smaller. At the same time, if the average difference in heating rate at the middle of the sintering furnace between the current sintering process and all subsequent sintering processes in the good cluster is smaller, it indicates that the heating rate of the current sintering process is highly consistent with the average of the good sintering process, the heating strategy is reasonable, and it is not easy to cause thermal stress problems, and the corresponding temperature rise deviation coefficient is smaller. The smaller the temperature rise deviation coefficient, the less likely the bars will accumulate thermal stress in the first heating stage of the current sintering process. In this case, the adjustment range of the heating rate can be appropriately reduced in subsequent heating stages, or even the original heating rate can be maintained, which helps to improve production efficiency while ensuring sintering quality.

[0062] Furthermore, this embodiment uses the temperature rise deviation coefficient of the first heating stage in the current sintering process to regulate the heating rate of subsequent heating stages in the current sintering process, specifically as follows: As one implementation method, in this embodiment, the heating rate of the next heating stage after the first heating stage in the current sintering process is... The expression is: In the formula, This indicates the preset initial heating rate for the next heating stage after the first heating stage in the current sintering process; This indicates the preset rate adjustment value; This represents the temperature rise deviation coefficient during the first heating stage of the current sintering process; norm() represents the normalization function.

[0063] The heating rate is iterated according to the above-mentioned process of adjusting the heating rate of the next heating stage, and all heating stages after the first heating stage in the current sintering process are traversed and the heating rate is adjusted accordingly.

[0064] It should be noted that the preset initial heating rate for the next heating stage after the first heating stage in the current sintering process, i.e. the initial heating rate during the process of raising the temperature to 800℃, ranges from 8 to 13℃ / min, and is set to 10℃ / min in this embodiment; the initial heating rate during the process of raising the temperature to 1350℃ ranges from 6.5 to 7.5℃ / min, and is set to 7℃ / min in this embodiment; the initial heating rate during the process of raising the temperature from 1250℃ to 1450℃ ranges from 2 to 3℃ / min, and is set to 2.5℃ / min in this embodiment.

[0065] In addition, it should be noted that the preset rate adjustment value is also set manually. In this embodiment, the preset rate adjustment value is 5. In actual application, the implementer can also set it according to the specific situation. This embodiment does not impose any special restrictions.

[0066] Thus, this embodiment combines historical good sintering process data to construct a temperature rise deviation coefficient to dynamically assess the degree of deviation between the current sintering process and the historical excellent state, and intelligently adjusts the heating rate of subsequent heating stages accordingly, effectively reducing the risk of thermal stress accumulation caused by temperature gradient, and significantly improving the sintering quality and production efficiency of cemented carbide rods.

[0067] Example 2 Example 2 provides a vacuum sintering process for preventing deformation of cemented carbide rods. For details, please refer to [link / reference]. Figure 1 The method includes the following steps: S1: Prepare cemented carbide rod blanks and perform degumming treatment.

[0068] S2: Vacuum treatment is performed on the degummed bar stock. In this embodiment, the vacuum degree inside the sintering furnace is 0.5 Torr, and the remaining operations are the same as in Embodiment 1.

[0069] S3: The vacuum-sealed bar stock is sintered, and the heating rate during the sintering process is controlled.

[0070] In this embodiment, the cooling rate is 15℃ / min, and the rest of the operation is the same as in Embodiment 1.

[0071] Example 3 Example 3 provides a vacuum sintering process for preventing deformation of cemented carbide rods. For details, please refer to [link to example]. Figure 1 The method includes the following steps: S1: Prepare cemented carbide rod blanks and perform degumming treatment.

[0072] S2: Vacuum treatment is performed on the degummed bar stock. In this embodiment, the vacuum degree inside the sintering furnace is 0.7 Torr, and the remaining operations are the same as in Embodiment 1.

[0073] S3: The vacuum-sealed bar stock is sintered, and the heating rate during the sintering process is controlled.

[0074] In this embodiment, the cooling rate is 15℃ / min, and the rest of the operation is the same as in Embodiment 1.

[0075] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments of this specification have been described above. Additionally, the processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired results. In some implementations, multitasking and parallel processing are possible or may be advantageous.

[0076] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0077] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions of some of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A vacuum sintering process for cemented carbide rods to prevent deformation, characterized in that, The process includes the following steps: S1: Prepare cemented carbide rod blanks and perform degumming treatment; S2: Vacuum treatment is performed on the degummed bar stock; S3: The vacuum-sealed bar stock is sintered, and the heating rate during the sintering process is controlled, specifically as follows: The temperature at each preset height inside the sintering furnace is acquired in real time during each sintering process, where each height refers to the top, middle and bottom of the sintering furnace; Based on the dispersion of temperature at all heights in the sintering furnace at each moment during each sintering process, the moments with significant temperature differences in each sintering process are screened out; based on the proportion of all moments with significant temperature differences in the first heating stage in each sintering process, and combined with the dispersion of temperature at all heights in the sintering furnace at each moment with significant temperature differences in the first heating stage, the furnace temperature deviation factor of the first heating stage in each sintering process is determined. Based on the correlation between the temperature of the parts of the sintering furnace and the top and bottom at all times during the first heating stage in each sintering process, and the number of clusters obtained by clustering at all times with significant temperature differences during the first heating stage, and combined with the furnace temperature deviation factor, the temperature imbalance coefficient of the first heating stage in each sintering process is determined. A number of sintering processes prior to the current sintering process are clustered to obtain a good cluster. Based on the difference in temperature imbalance coefficient of the first heating stage between the current sintering process and all sintering processes in the good cluster, as well as the difference in heating rate in the middle of the sintering furnace, the temperature rise deviation coefficient of the first heating stage in the current sintering process is determined, so as to regulate the heating rate of the subsequent heating stages in the current sintering process.

2. The vacuum sintering process for preventing deformation of cemented carbide rods as described in claim 1, characterized in that, The vacuum level during the vacuuming process ranges from 0.3 to 0.7 Torr.

3. The vacuum sintering process for preventing deformation of cemented carbide rods as described in claim 1, characterized in that, The initial heating time is set to 55-60 minutes.

4. The vacuum sintering process for preventing deformation of cemented carbide rods as described in claim 1, characterized in that, The cooling rate during the cooling stage of the sintering process ranges from 11 to 30 °C / min.

5. The vacuum sintering process for preventing deformation of cemented carbide rods as described in claim 1, characterized in that, The screening of moments with significant temperature differences during each sintering process includes: The degree of temperature dispersion at all heights inside the sintering furnace at each moment during each sintering process is recorded as the temperature dispersion value for each sintering process. The discrete temperature values ​​at all times during each sintering process are used as input to the threshold segmentation algorithm, and the output is the segmentation threshold. The times when the discrete temperature values ​​are greater than or equal to the segmentation threshold are taken as the times when the temperature difference is significant during each sintering process.

6. The vacuum sintering process for preventing deformation of cemented carbide rods as described in claim 5, characterized in that, The expression for the furnace temperature deviation factor during the first heating stage of each sintering process is as follows: In the formula, This represents the furnace temperature deviation factor during the first heating stage in the i-th sintering process; This represents the percentage of all significant temperature differences during the first heating stage in the i-th sintering process out of all possible times. It represents the mean of the discrete values ​​of temperature at all significant temperature differences during the first heating stage in the i-th sintering process.

7. The vacuum sintering process for preventing deformation of cemented carbide rods as described in claim 1, characterized in that, The method for determining the temperature imbalance coefficient during the first heating stage in each sintering process is as follows: Calculate the cross-correlation sequence of temperatures between the middle part and the top and bottom of the sintering furnace at all times during the first heating stage in each sintering process. The time delay corresponding to the maximum value in the cross-correlation sequence of temperatures between the middle and the top is denoted as the first time delay, and the time delay corresponding to the maximum value in the cross-correlation sequence of temperatures between the middle and the bottom is denoted as the second time delay. The difference between the first time delay and the second time delay is denoted as the time delay difference of the first heating stage in each sintering process. The number of clusters obtained by clustering all significant temperature differences during the first heating stage is denoted as the cluster number. The product of the time lag difference of the first heating stage and the furnace temperature deviation factor in each sintering process is multiplied by the cluster number, and the result is used as the temperature imbalance coefficient of the first heating stage in each sintering process.

8. The vacuum sintering process for preventing deformation of cemented carbide rods as described in claim 1, characterized in that, The method of clustering a preset number of sintering processes prior to the current sintering process to obtain well-formed clusters includes: Obtain the deformation rate of the bar at the end of each sintering process, cluster the sintering processes that were previously sintered a preset number of times, where the metric distance of the clustering process is set to the absolute value of the difference in the deformation rate of the bar between sintering processes, output all clusters, calculate the mean value of the deformation rate of the bar in all sintering processes within each cluster, and record it as the mean deformation rate. The cluster corresponding to the minimum mean deformation rate is taken as the good cluster of the current sintering process.

9. The vacuum sintering process for preventing deformation of cemented carbide rods as described in claim 1, characterized in that, The expression for the temperature rise deviation coefficient during the first heating stage of the current sintering process is as follows: In the formula, This represents the temperature rise deviation coefficient during the first heating stage of the current sintering process; This represents the minimum difference in temperature imbalance coefficients during the first heating stage between the current sintering process and all subsequent sintering processes in the good cluster; This represents the average difference in heating rate at the center of the sintering furnace between the current sintering process and all subsequent sintering processes in the good cluster.

10. The vacuum sintering process for preventing deformation of cemented carbide rods as described in claim 1, characterized in that, The regulation of the heating rate in the subsequent heating stages of the current sintering process includes: The heating rate of the next heating stage after the first heating stage in the current sintering process The expression is: In the formula, This indicates the preset initial heating rate for the next heating stage after the first heating stage in the current sintering process; This indicates the preset rate adjustment value; This represents the temperature rise deviation coefficient during the first heating stage of the current sintering process; norm() represents the normalization function; The heating rate is iterated according to the above-mentioned process of adjusting the heating rate of the next heating stage, and all heating stages after the first heating stage in the current sintering process are traversed and the heating rate is adjusted accordingly.

Images